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Gandasi, N. R., Yin, P., Riz, M., Chibalina, M. V., Cortese, G., Lund, P.-E., . . . Barg, S. (2017). Ca2+ channel clustering with insulin-containing granules is disturbed in type 2 diabetes. Journal of Clinical Investigation, 127(6), 2353-2364.
Open this publication in new window or tab >>Ca2+ channel clustering with insulin-containing granules is disturbed in type 2 diabetes
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2017 (English)In: Journal of Clinical Investigation, ISSN 0021-9738, E-ISSN 1558-8238, Vol. 127, no 6, p. 2353-2364Article in journal (Refereed) Published
Abstract [en]

Loss of first-phase insulin secretion is an early sign of developing type 2 diabetes (T2D). Ca2+ entry through voltage-gated L-type Ca2+ channels triggers exocytosis of insulin-containing granules in pancreatic β cells and is required for the postprandial spike in insulin secretion. Using high-resolution microscopy, we have identified a subset of docked insulin granules in human β cells and rat-derived clonal insulin 1 (INS1) cells for which localized Ca2+ influx triggers exocytosis with high probability and minimal latency. This immediately releasable pool (IRP) of granules, identified both structurally and functionally, was absent in β cells from human T2D donors and in INS1 cells cultured in fatty acids that mimic the diabetic state. Upon arrival at the plasma membrane, IRP granules slowly associated with 15 to 20 L-type channels. We determined that recruitment depended on a direct interaction with the synaptic protein Munc13, because expression of the II-III loop of the channel, the C2 domain of Munc13-1, or of Munc13-1 with a mutated C2 domain all disrupted L-type channel clustering at granules and ablated fast exocytosis. Thus, rapid insulin secretion requires Munc13-mediated recruitment of L-type Ca2+ channels in close proximity to insulin granules. Loss of this organization underlies disturbed insulin secretion kinetics in T2D.

National Category
Cell and Molecular Biology
Research subject
Molecular Cellbiology
Identifiers
urn:nbn:se:uu:diva-321935 (URN)10.1172/JCI88491 (DOI)000402620800029 ()28481223 (PubMedID)
Funder
Swedish Research CouncilSwedish Diabetes AssociationThe Swedish Brain FoundationSwedish Child Diabetes FoundationEXODIAB - Excellence of Diabetes Research in SwedenNovo Nordisk
Available from: 2017-05-12 Created: 2017-05-12 Last updated: 2018-01-13Bibliographically approved
Salunkhe, V. A., Ofori, J. K., Gandasi, N. R., Salo, S. A., Hansson, S., Andersson, M. E., . . . Eliasson, L. (2017). MiR-335 overexpression impairs insulin secretion through defective priming of insulin vesicles. Physiological Reports, 5(21), Article ID e13493.
Open this publication in new window or tab >>MiR-335 overexpression impairs insulin secretion through defective priming of insulin vesicles
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2017 (English)In: Physiological Reports, E-ISSN 2051-817X, Vol. 5, no 21, article id e13493Article in journal (Refereed) Published
Abstract [en]

MicroRNAs contribute to the maintenance of optimal cellular functions by fine-tuning protein expression levels. In the pancreatic beta-cells, imbalances in the exocytotic machinery components lead to impaired insulin secretion and type 2 diabetes (T2D). We hypothesize that dysregulated miRNA expression exacerbates beta-cell dysfunction, and have earlier shown that islets from the diabetic GK-rat model have increased expression of miRNAs, including miR-335-5p (miR-335). Here, we aim to determine the specific role of miR-335 during development of T2D, and the influence of this miRNA on glucose-stimulated insulin secretion and Ca2+-dependent exocytosis. We found that the expression of miR-335 negatively correlated with secretion index in human islets of individuals with prediabetes. Overexpression of miR-335 in human EndoC-beta H1 and in rat INS-1 832/13 cells (OE335) resulted in decreased glucose-stimulated insulin secretion, and OE335 cells showed concomitant reduction in three exocytotic proteins: SNAP25, Syntaxin-binding protein 1 (STXBP1), and synaptotagmin 11 (SYT11). Single-cell capacitance measurements, complemented with TIRF microscopy of the granule marker NPY-mEGFP demonstrated a significant reduction in exocytosis in OE335 cells. The reduction was not associated with defective docking or decreased Ca2+ current. More likely, it is a direct consequence of impaired priming of already docked granules. Earlier reports have proposed reduced granular priming as the cause of reduced first-phase insulin secretion during prediabetes. Here, we show a specific role of miR-335 in regulating insulin secretion during this transition period. Moreover, we can conclude that miR-335 has the capacity to modulate insulin secretion and Ca2+-dependent exocytosis through effects on granular priming.

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
Keyword
Beta cell, exocytosis, insulin secretion, microRNA, patch-clamp, SNAP25, STXBP1, TIRF, Type 2 Diabetes
National Category
Physiology
Identifiers
urn:nbn:se:uu:diva-339717 (URN)10.14814/phy2.13493 (DOI)000415351500008 ()
Available from: 2018-01-26 Created: 2018-01-26 Last updated: 2018-01-26Bibliographically approved
Marshall, M., Lund, P.-E. & Barg, S. (2017). Molecular Mechanisms of V-SNARE Function in Secretory Granule Exocytosis. Paper presented at 58th Annual Meeting of the Biophysical-Society, FEB 15-19, 2014, San Francisco, CA. Biophysical Journal, 112(3), 395A-395A.
Open this publication in new window or tab >>Molecular Mechanisms of V-SNARE Function in Secretory Granule Exocytosis
2017 (English)In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 112, no 3, p. 395A-395AArticle in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
CELL PRESS, 2017
National Category
Biophysics
Identifiers
urn:nbn:se:uu:diva-332760 (URN)000402375600962 ()
Conference
58th Annual Meeting of the Biophysical-Society, FEB 15-19, 2014, San Francisco, CA
Available from: 2017-11-06 Created: 2017-11-06 Last updated: 2017-11-06
Alenkvist, I., Gandasi, N. R., Barg, S. & Tengholm, A. (2017). Recruitment of Epac2A to Insulin Granule Docking Sites Regulates Priming for Exocytosis. Diabetes, 66(10), 2610-2622.
Open this publication in new window or tab >>Recruitment of Epac2A to Insulin Granule Docking Sites Regulates Priming for Exocytosis
2017 (English)In: Diabetes, ISSN 0012-1797, E-ISSN 1939-327X, Vol. 66, no 10, p. 2610-2622Article in journal (Refereed) Published
Abstract [en]

Epac is a cAMP-activated guanine nucleotide exchange factor that mediates cAMP signaling in various types of cells, including -cells, where it is involved in the control of insulin secretion. Upon activation, the protein redistributes to the plasma membrane, but the underlying molecular mechanisms and functional consequences are unclear. Using quantitative high-resolution microscopy, we found that cAMP elevation caused rapid binding of Epac2A to the -cell plasma membrane, where it accumulated specifically at secretory granules and rendered them more prone to undergo exocytosis. cAMP-dependent membrane binding required the high-affinity cyclic nucleotide-binding (CNB) and Ras association domains, but not the disheveled-Egl-10-pleckstrin domain. Although the N-terminal low-affinity CNB domain (CNB-A) was dispensable for the translocation to the membrane, it was critical for directing Epac2A to the granule sites. Epac1, which lacks the CNB-A domain, was recruited to the plasma membrane but did not accumulate at granules. We conclude that Epac2A controls secretory granule release by binding to the exocytosis machinery, an effect that is enhanced by prior cAMP-dependent accumulation of the protein at the plasma membrane.

National Category
Clinical Medicine
Identifiers
urn:nbn:se:uu:diva-336299 (URN)10.2337/db17-0050 (DOI)000411195800009 ()28679628 (PubMedID)
Note

De två första författarna delar förstaförfattarskapet.

Available from: 2018-01-23 Created: 2018-01-23 Last updated: 2018-01-23Bibliographically approved
Barg, S. & Gucek, A. (2016). How Kiss-and-Run Can Make Us Sick: SOX4 Puts a Break on the Pore. Diabetes, 65(7), 1791-1793.
Open this publication in new window or tab >>How Kiss-and-Run Can Make Us Sick: SOX4 Puts a Break on the Pore
2016 (English)In: Diabetes, ISSN 0012-1797, E-ISSN 1939-327X, Vol. 65, no 7, p. 1791-1793Article in journal, Editorial material (Other academic) Published
National Category
Endocrinology and Diabetes
Identifiers
urn:nbn:se:uu:diva-300622 (URN)10.2337/dbi16-0019 (DOI)000378463000005 ()27329955 (PubMedID)
Available from: 2016-08-10 Created: 2016-08-10 Last updated: 2017-11-28Bibliographically approved
Alenkvist, I., Gandasi, N. R., Barg, S. & Tengholm, A. (2015). Activation-dependent translocation of Epac2 to granule docking sites at the beta cell plasma membrane. Paper presented at 51st Annual Meeting of the European-Association-for-the-Study-of-Diabetes (EASD), SEP 14-18, 2015, Stockholm, SWEDEN. Diabetologia, 58(Suppl. 1), S210-S210.
Open this publication in new window or tab >>Activation-dependent translocation of Epac2 to granule docking sites at the beta cell plasma membrane
2015 (English)In: Diabetologia, ISSN 0012-186X, E-ISSN 1432-0428, Vol. 58, no Suppl. 1, p. S210-S210Article in journal, Meeting abstract (Other academic) Published
National Category
Endocrinology and Diabetes
Identifiers
urn:nbn:se:uu:diva-264887 (URN)000359820901111 ()
Conference
51st Annual Meeting of the European-Association-for-the-Study-of-Diabetes (EASD), SEP 14-18, 2015, Stockholm, SWEDEN
Note

Meeting Abstract: 421

Available from: 2015-11-05 Created: 2015-10-19 Last updated: 2017-12-01Bibliographically approved
Yin, P., Gandasi, N. R., Riz, M., Cortese, G., Chibalina, M., Rorsman, P., . . . Barg, S. (2015). Clustering of L-type CA(2+)-channels promotes exocytosis of individual secretory granules. Paper presented at 51st Annual Meeting of the European-Association-for-the-Study-of-Diabetes (EASD), SEP 14-18, 2015, Stockholm, SWEDEN. Diabetologia, 58(Suppl. 1), S128-S128.
Open this publication in new window or tab >>Clustering of L-type CA(2+)-channels promotes exocytosis of individual secretory granules
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2015 (English)In: Diabetologia, ISSN 0012-186X, E-ISSN 1432-0428, Vol. 58, no Suppl. 1, p. S128-S128Article in journal, Meeting abstract (Other academic) Published
National Category
Endocrinology and Diabetes
Identifiers
urn:nbn:se:uu:diva-264915 (URN)000359820900255 ()
Conference
51st Annual Meeting of the European-Association-for-the-Study-of-Diabetes (EASD), SEP 14-18, 2015, Stockholm, SWEDEN
Note

Meeting Abstract: 254

Available from: 2015-11-04 Created: 2015-10-19 Last updated: 2017-12-01Bibliographically approved
Kay, E. I. & Barg, S. (2015). G-protein coupled receptor dynamics in insulin secreting cells. Paper presented at 51st Annual Meeting of the European-Association-for-the-Study-of-Diabetes (EASD), SEP 14-18, 2015, Stockholm, SWEDEN. Diabetologia, 58(Suppl. 1), S212-S212.
Open this publication in new window or tab >>G-protein coupled receptor dynamics in insulin secreting cells
2015 (English)In: Diabetologia, ISSN 0012-186X, E-ISSN 1432-0428, Vol. 58, no Suppl. 1, p. S212-S212Article in journal, Meeting abstract (Other academic) Published
National Category
Endocrinology and Diabetes
Identifiers
urn:nbn:se:uu:diva-264903 (URN)000359820901116 ()
Conference
51st Annual Meeting of the European-Association-for-the-Study-of-Diabetes (EASD), SEP 14-18, 2015, Stockholm, SWEDEN
Note

Meeting Abstract: 426

Available from: 2015-11-05 Created: 2015-10-19 Last updated: 2017-12-01Bibliographically approved
Salunkhe, V. A., Ofori, J., Gandasi, N. R., Salo, S. A., Hansson, S., Andersson, M. E., . . . Eliasson, L. (2015). MiR-335 regulates exocytotic proteins and affects glucose-stimulated insulin secretion through decreased Ca2+-dependent exocytosis in beta cells. Paper presented at 51st Annual Meeting of the European-Association-for-the-Study-of-Diabetes (EASD), SEP 14-18, 2015, Stockholm, SWEDEN. Diabetologia, 58(Suppl. 1), S128-S128.
Open this publication in new window or tab >>MiR-335 regulates exocytotic proteins and affects glucose-stimulated insulin secretion through decreased Ca2+-dependent exocytosis in beta cells
Show others...
2015 (English)In: Diabetologia, ISSN 0012-186X, E-ISSN 1432-0428, Vol. 58, no Suppl. 1, p. S128-S128Article in journal, Meeting abstract (Other academic) Published
National Category
Endocrinology and Diabetes
Identifiers
urn:nbn:se:uu:diva-264912 (URN)000359820900256 ()
Conference
51st Annual Meeting of the European-Association-for-the-Study-of-Diabetes (EASD), SEP 14-18, 2015, Stockholm, SWEDEN
Note

Meeting Abstract: 255

Available from: 2015-11-04 Created: 2015-10-19 Last updated: 2017-12-01Bibliographically approved
Gandasi, N. R. & Barg, S. (2015). Quantitative Imaging of the Exocytosis Machinery Assembly. Biophysical Journal, 108(2), 102A-102A.
Open this publication in new window or tab >>Quantitative Imaging of the Exocytosis Machinery Assembly
2015 (English)In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 108, no 2, p. 102A-102AArticle in journal, Meeting abstract (Other academic) Published
National Category
Biophysics
Identifiers
urn:nbn:se:uu:diva-274842 (URN)000359471700514 ()
Available from: 2016-01-26 Created: 2016-01-26 Last updated: 2017-11-30Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4661-5724

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